1. Field of the Invention
The present invention relates to semiconductor integrated displays and methods of making such displays.
2. Description of Related Art
In recent years, it has been proposed to integrate small passive displays of the electrochomic or liquid crystal type with an addressable matrix of transistors formed in a silicon or other semiconductor substrate. In such displays, the picture elements (pels) are formed in a corresponding matrix and each element is connected to a respective one of the transistors, which controls its operation. Such displays, up to and including the picture elements, are built employing techniques analogous to those employed in semiconductor integrated circuit manufacturing.
One severe problem encountered with these displays is the lack of contrast between the display in the switched on and switched off modes owing to the gaps between the pels. The gaps between the pels are necessary to electrically insulate one pel from its immediate neighbors. However, although such gaps are small, the cumulative effect of the large number of gaps produces a dark coloration background to the display giving the lack of contrast between the switched on and switched off modes. European patent publication EP-A-0112417 discloses a semiconductor integrated display and method for making the same in which the display electrodes are formed from a layer of silver evaporated over the entire upper surface of a partially formed display and gaps between the individual electrodes are subsequently made by sputter etching. The width of the gaps between each electrode and its immediate neighbors is dictated by the need to electrically isolate each electrode from its neighbors and by the present state of the art of the technique of sputter etching.
A further problem encountered in such displays is that of photoconduction in the semiconductor substrate. If light, which illuminates the display for viewing or projection, penetrates to the substrate, the resulting photoconduction can produce undesirable electrical leakage paths. As a result unselected areas of the display can become colored or the coloration of selected areas of the display can fade. This problem has been recognized in the art and various proposals made to overcome it. One suitable method of overcoming this problem is disclosed in European patent publication EP-A-0112417 and utilizes a metallic light barrier which is at least co-extensive with the gaps between the display electrodes and the semiconductor substrate.